# Electronic structure for new layered high-temperature superconductors CaAFe4As4 (A=K, Rb, Cs): FLAPW-GGA calculations

## TL;DR

This study uses first-principles calculations to analyze the electronic structure and bonding in newly synthesized layered high-temperature superconductors CaAFe4As4 (A=K, Rb, Cs), revealing their complex Fermi surfaces and bonding characteristics.

## Contribution

First detailed electronic structure analysis of CaAFe4As4 superconductors using FLAPW-GGA, providing insights into their bonding and Fermi surface topology.

## Key findings

- Fermi surfaces are multisheet with cylindrical features.
- Bonding involves metallic, covalent, and ionic contributions.
- Superconductivity correlates with bond angles and anion height.

## Abstract

Recently, new FeAs based high-temperature superconductors CaAFe4As4 (A=K, Rb, Cs) with a layered tetragonal crystal structure were synthesized (TC ~ 30 K). In this Letter, we report for the first time the band structures, Fermi surface topology, total and partial densities of electronic states and interatomic interactions for CaAFe4As4 as estimated by means of the first-principles FLAPW-GGA calculations. The interatomic bonding picture can be represented as a highly anisotropic mixture of metallic, covalent, and ionic contributions, which are realized inside Fe4As4 layered blocks and between these blocks and Ca, A atomic sheets. The Fermi surfaces of these systems have a multisheet character and are compiled of a large number of cylinders at the edges and in the central part of the Brillouin zone. It is established that the high-temperature superconductivity in CaAFe4As4 compounds as in other related systems correlates well with such structure parameters as bond angles and anion height.

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Source: https://tomesphere.com/paper/1706.02642